Limit switch control having switch mounting means



Aug. 12, 1969 D. R. JACOBS 3,461,254

LIMIT SWITCH CONTROL HAVING SWITCH MOUNTING MEANS Filed Feb. 27, 1967 Z SheetS-Sheet l llllllll 33 34- jnvenh'rs jjamfd EJ255226 KB 1 D. R. JACOBS Aug. 12, 1969 LIMIT SWITCH CONTROL HAVING SWITCH MOUNTING MEANS 2 Sheets-Sheet 2 United States Patent 3,461,254 LIMIT SWITCH CONTROL HAVING SWITCH MOUNTING MEANS David R. Jacobs, Blulfton, Ind., assignor to Franklin Electric Co., Inc., Bluifton, Ind., a corporation of Indiana Filed Feb. 27, 1967, Ser. No. 618,764 Int. Cl. Htllh 3/16, 9/02 U.S. Cl. 200-47 7 Claims ABSTRACT OF THE DISCLOSURE This disclosure deals with a limit switch control for a drive unit which includes a power output shaft. The control includes two cams which are connected by a wormgear arrangement to be rotated by the power output shaft. Two plungers are located to be moved by the two cams, and each plunger actuates a limit switch upon movement thereof. The control further includes a molded case which houses and supports the cams, plungers and switch parts of the drive unit.

Applicants copending patent application Ser. No. 453; 587, filed May 6, 1965 and entitled Limit Switch Control For A Motor Drive, now Patent No. 3,306,997, describes a limit switch control including a pair of relatively adjustable cam members connected through a worm-gear to be driven by the motor. The cam members are rotatably mounted in a housing for the control and are adapted to actuate a pair of microswitches of conventional form upon rotation.

While the foregoing mechanism operates very well, it is relatively expensive since a machined metal housing is employed and a relatively expensive type of switch structure is required.

Accordingly it is an object of this invention to provide a limit switch control of the general character described in the above application, but including a pair of cam members connected to be rotated by the motor drive, a pair of inexpensive simply constructed switches, plungers movable by the cam members for actuating the switches, and a plastic case for the foregoing parts. In addition to housing the foregoing parts, the case also serves to rotatably support the cam members, properly locate the parts relative to the motor drive, support the parts of the switches, and support the plungers for sliding movement into and out of engagement with the switches. The case and the parts mounted thereon form a complete assembly which may be used with different types of motor drives.

Objects and advantages of the invention will become apparent from the following description taken in conjunction with the accompanying figures of the drawings, in which:

FIG. 1 is a perspective view of a motor drive unit including a limit switch control constructed in accordance with the invention;

FIG. 2 is an enlarged view showing a portion of the motor drive unit with the limit switch control therein;

FIG. 3 is an enlarged exploded perspective view of a portion of the limit switch control;

FIG. 4 is a sectional view taken on the line 22 of FIG. 2;

FIG. 5 is a fragmentary sectional View taken on the line 55 of FIG. 4;

FIG. 6 is an enlarged view of the limit switch control with some of the parts removed, and mounted in the motor drive unit;

FIG. 7 is a sectional view taken on the line 7-7 of FIG. 6;

FIG. 8 is a fragmentary sectional view taken on the line 8-8 of FIG. 6; and

FIG. 9 is a fragmentary sectional view taken on the line 9-9 of FIG. 6.

In greater detail, in FIG. 1 there is shown a motor, indicated by the numeral 10, having a rotor shaft (not shown). The rotor shaft is connected through a gear box 11 to a cam drive shaft 12, which may be either an extension of the power output shaft of the motor-gear box unit or a shaft connected to be rotated by the power output shaft. Formed on the side of the gear box 11 is a control housing portion 13 which contains a limit switch control 14. A cover 19 cooperates with the portion 13 to enclose the control 14, and is fastened to the portion 13 by a plurality of bolts 16.

The limit switch control 14 includes a limit shaft 26 which is journaled at its ends in a case 17. Mounted on the limit shaft 26 are an adjustable face cam member 33 (FIGS. 3 and 7) and a fixed face cam member 34, the former cam member 33 being secured to the limit shaft 26, as by knurling a portion 30 of the surface of the shaft 26 and pressing the member 33 on the knurled portion, and the latter cam member 34 being loosely mounted on the limit shaft 26. A compression spring 36 is positioned around the limit shaft 26 between the cam member 34 and a snap ring 35, and urges the fixed cam member 34 toward the adjustable cam member 33. The snap ring 35 is positioned around the shaft 26 in a groove 35a formed in the shaft 26, and a washer 35b is positioned between the other end of the spring 36 and the cam member 34. When the terms fixed and adjustable are used herein with regard to the two cam members 34 and 33, it is meant that the cam member 33 is adjustable in the rotary direction with the shaft 26 but is substantially stationary in the axial direction, while the cam member 34 is fixed against rotation by the worm on the shaft 12 but is axially movable relative to the shaft 26 as the latter is rotated for adjustment.

One end of the cam drive shaft 12 extends into the limit switch control case 17 adjacent the cam member 34 (FIGS. 2 and 5) and this end of the shaft 12 has a worm 37 formed on it. The cam member 34 is cylindrical and its outer surface has axially extending gear teeth 38 formed on it, which mesh with the worm 37 of the shaft 12. Therefore, rotation of the cam drive shaft 12 also causes rotary movement of the cam member 34.

The two cam members 33 and 34 are adjustably connected together by a clutch arrangement including similar sets of V-shaped radially extending clutch teeth 41 and 42 formed on the cam members 33 and 34, respectively. The members 33 and 34 may, for example, be molded plastic members. The cam member 34 is shown as having an annular flange 43 (FIG. 7) at its outer periphery, the flange 43 extending around an annular axially extending flange 44 formed on the cam member 33. The adjacent surfaces of the flanges 43 and 44 act as a guide during movement of the cam member 34 relative to the cam member 33. The clutch teeth 41 and 42 are formed on the outer radially extending surface of the flange 44 and on an adjacent radially extending surface of the cam member 34. The members 33 and 34 are also provided with hubs 46 and 47, respectively, which engage the shaft 26, and the interior of the members 33 and 34 may be recessed between the surfaces having the teeth 41 and 42, and the hubs 46 and 47.

The spring 36 urges the cam members together and tends to hold the teeth 41 and 42 in engagement. When the teeth 41 and 42 are engaged as shown in FIGS. 2, 4 and 7, rotation of the cam drive shaft 12 causes rotation of the cam member 34 due to the connection between the worm gear 37 and gear teeth 38, and the clutch connection, including the sets of teeth 41 and 42, imparts motion from the cam member 34 to the cam members 33 and the limit shaft 26.

The two cam members 33 and 34 are respectively provided with raised cam surfaces 51 and 52 on their radial faces which are away from the teeth 41 and 42. Two switches 21 and 22 are provided along with movable actuating plungers 53 and 54, respectively, and the cam surfaces 52 and 51 are engageable with the two plungers 53 and 54 which in turn are engageable with the switches 21 and 22. Upon rotation of the limit shaft 26 and the two cam members 33 and 34 in one direction, the cam surface 52 engages the plunger 53 and actuates the switch 21, and upon rotation of the limit shaft 26 in the opposite direction, the cam surface 51 engages the plunger 54 and actuates the other switch 22. The drive motor 10 is connected in a conventional manner to be energized through the switches 21 and 22, and engagement by the plungers 53 and 54 opens the switches 21 and 22. Therefore, if the drive motor 10 is energized for rotation in one direction, energization will continue until the cam member 52 engages the plungers 53 and actuates the limit switch 21 to turn off the motor. Energization of the motor 10 in the opposite direction rotates the limit shaft 26 and the two cam members in the opposite direction until the raised cam surface 51 engages the other plunger 54 and actuates the switch 22 and again deenergizes the motor 10.

It will be apparent that the number of revolutions of the motor 10 required to go from one limit to the other, depends upon the gear ratio between the worm 37 and the gear teeth and the angular separation between the two earns 51 and 52.

The construction of the teeth 41 and 42 of the clutch and the construction of the worm 37 and gear 38 teeth are preferably such that the angular separation between adjacent teeth of each set of teeth 41 and 42, is equal to the angular displacement of the two cam members 33 and 34 due to one complete revolution drive shaft 12. Therefore, when adjusting the position of the cam member 33 relative to the cam member 34, the number of revolutions of the drive shaft 12 to be increased or decreased is first determined and the two cam members 33 and 34 are then angularly displaced a corresponding number of clutch teeth 41 and 42. To aid in case of adjustment of one of the cam members relative to the other of the cam members, at least one end of the limit shaft 26 is provided with a screwdriver receiving slot 56. As will be explained hereinafter, the slotted ends of the shaft 26 are located in holes formed through the housing portion 13, so that the limit switch control 14 may be adjusted without removing the cover 19.

The case 17 of the control 14 comprises a substantially flat base 61 (FIGS. 4 to 9) having a hole 62 formed therein through which the saft 12 extends. With reference to FIG. 8, an interior wall 63 is formed within the gear box 11 adjacent the portion 13, and a hole 64 for the shaft 12 is also formed in the wall 63. The control 14 is located with the hole 62 overlying the hole 64 which is the larger of the two. A circular locating rabbet or flange 66 is formed on the back side of the base 61, and the flange 66 extends into the hole 64 in order to properly align the limit switch control relative to the shaft 12. A rearwardly extending tapered projection 67 (FIGS. 4 and 8) may also be formed on the back side of the base 61, the projection 67 preferably extending into a mating cavity 65 in the wall 63 in order to angularly align the limit switch control with the shaft 12.

To rotatably support the shaft 26 and the cam members 33 and 34 on the case 17, a bearing post 68 and two clip posts 69 and 70 (FIGS. and 6) are formed on the front side and adjacent the right hand edge of the base 61 as seen in FIG. 6, and a bearing post 72 and two clip posts 73 and 74 are formed on the front side and adajacent the left hand edge of the base 61. The posts extends forwardly from the base 61 and rotatably support the shaft 26 in spaced relation therefrom. The outer or forward ends of the bearing posts 68 and 72 have semi-circular recesses 71 formed therein, the recesses having substant' ially the same curvature as the shaft 26 and receiving this shaft. As shown in FIGS. 5 and 9, the forward ends of the clip posts extend beyond the ends of the bearing posts, and the sides of the clip posts, which are adjacent the bearing posts, include projections or clips 73 which project partially over the bearing posts. The forwardmost edges 74 of the clips 73 slant rearwardly and toward the associated bearing post which the rearwardmost edges 76 of the clips 73 slant forwardly and toward the associated bearing posts, the edges 74 and 76 meeting at peaks 73a (FIG. 9). The minimum distance between the peaks 73a of each pair of clip posts when in their normal or unflexed condition is less than the thickness of the shaft 26. Further, in the absence of the shaft 26, the edges 76 are spaced from the recesses 71 a distance which is slightly less than the thickness of the shaft 26. The clip posts are relatively flexible, and the shaft 26 may be located in the recess 71 of each bearing post by positioning the shaft 26 against the edges 74 of the clip posts and applying enough rearward pressure on the shaft 26 to flex or earn the clip posts apart. Once the shaft 26 is moved rearwardly past the peaks 73a and is seated in the recesses 71, the clip posts flex toward each other and the shaft by the edges 76. Sufficient forward pressure may be applied to the shaft to cam the clip posts apart in order to release the shaft 26. To prevent axial movement of the shaft 26 and the cam members relative to the case 17, a circular groove 78 (FIGS. 3 and 7) is formed in the shaft 26 adjacent the bearing post 72, and a ridge 77 is formed in the recess 71 of the post 72, the groove 78 receiving the ridge 77 and thereby preventing axial movement of the shaft 26. With the exception of the ridge 77, the case 17 is symmetrical about avertical center line as seen in FIGS. 2 and 6.

With reference to FIGS. 2, 6, 7 and 9, the switches 21 and 22 are respectively located in enclosures 81 and 82. The enclosure 82, which is identical with the enclosure 81, comprises four forwardly extending walls 83, 84, 85 and 86 and a cover 87 (FIGS. 2 and 9), the walls 83 to 86 being formed integrally with each other and with the base 61, and the cover 87 being secured within the walls.

The switch 22, which is similar to the switch 21, includes a stationary contact 91 which is secured as by welding to a stationary contact arm 92. To fasten the arm 92 to the base 61, forwardly extending grooves 93 and 94 are formed in the walls 83 and 86, having a width which is substantially equal to the thickness of the arm 92. The arm 92 may thus be fastened to the case by positioning the forwardly extending edges of the arm 92 in the grooves with the contact 91 facing away from the walls 83, and pushing the arm rearwardly in the grooves until the rearward edge of the arm 92 meets the base 61. One corner portion 96 of the arm 92 (FIGS. 3 and 8) extends forwardly out of the enclosure through a recess in the cover and is adapted to be secured to an external lead such as one of the two leads (FIG. 1).

The switch 22 also includes a movable contact 97 secured as by welding to one end of a movable contact arm 98 which extends out of the enclosure through a slot 99 formed in the wall 84. The outer end 100 of the arm 98 is also adapted to be secured to the other of the two leads 95. The two contacts 91 and 97 are located at the end of the enclosure which is adjacent the wall 86, and face each other, and the arm 98 is supported such that the switch contacts 91 and 97 are normally closed. The support for the arm 98 comprises one edge 101 of the slot 99, and an abutment 102 formed in the corner between the walls 84 and 85. The abutment 102 engages the side of the arm 98, which is away from the contact 97 and hows the center portion of the arm 98 in the direction of the edge 101 and the stationary contact 91, thus normally holding the contacts 91 and 97 closed. However, the arm is flexible and may be bowed to move the contact 97 out of engagement with the contact 91 as will be explained. Forward and rearward movement of the portion of the contact arm 98 adjacent the abutment 102 is normally prevented by a ridge 104 and the bottom of the slot 99, and by a ledge 106 which extends from the abutment 102 and overhangs the arm 98. Movement of the arm 98 in the direction of its length is prevented by making the depth of the slot 99 in the wall 84 such that the Wall will fit into a notch 98a formed in the arm 98 as shown in FIG. 9.

The cover 87 for the enclosure 82 has substantially 86. Narrow ledges 107 are formed on the inner sides of the walls 83. 85 and 86, and the cover 87 is seated on the ledges 107 and on the forward surface of the abutment 102, with the forward surface of the cover being substantially flush with the forward edges of the walls 83 to 86. The corner of the cover 87 which is adjacent the stationary contact arm 92 is notched to provide clearance for the portion 66 of the arm 92 as previously explained. To fasten the cover 87 to the case 17, a tab 108 (FIGS. 8 and 9) is formed on the end of the cover 87, which is adjacent the wall 86, and a slot 109 is formed in the wall 86 to receive the tab 108. The post 72, which is formed integrally with the wall 85, is undercut as at 111 and the cover extends into the undercut 111 and is releasably held thereby. Further, the cover is releasably fastened to the case and the case is fastened to the wall 63 by a screw 112 (FIGS. 2 and 9) which extends through a hole formed in the cover, through a hole 113 (FIG. 6) formed in the case 17, and into the wall 63.

The construction of the enclosure 81 and the cover for the other switch is the mirror image of the foregoing construction, and the same reference numerals are used for those parts.

As previously stated, the plungers 53 and 54 respectively actuate the two switches 21 and 22 in response to turning movement of the cam members 33 and 34. With reference to FIGS. 3 and 8, the two plungers extend parallel to the shaft 26 and are located between the shaft 26 and the base 61. Each plunger includes an elongated generally rectangular guide portion 121, and the two portions 121 are positioned in side-by-side relation within a slide channel formed by two forwardly extending walls 122 formed on the base 61. The walls 122 are substantially the same height as the portions 121 and guide the movement of the plungers 53 and 54. As shown in FIG. 6, openings 123 are formed in the walls 83 of the two switch enclosures, and the plungers 53 and 54 respectively extend through the openings 123 into the enclosures 81 and 82.

While the switches 21 and 22 could be either of the normally closed type or the normally open type in the present instance they are normally closed, and to actuate the switches 21 and 22 from the closed to the open position, the plungers 53 and 54 include cam follower portions 126 which extend forwardly from the outer ends of the guide portions 121 respectively into the space between the cam member 33 and the switch 22 and the space between the cam member 34 and the switch 21. As shown in FIG. 3 the forwardly extending outer edge 127 of each portion 126 engages the associated movable contact arm 98 while the inner edges 128 are engageable by the cams of the cam members. The outer edge 127 is slightly longer than the inner edge 128, thereby producing a stepped appearance as shown in FIG. 3. The forwardmost surface 129 of each enlarged portion is located within the associated switch enclosure and slidingly engages the inner or rearward surface of the associated cover 87. Such engagement holding the cam follower portions of the plungers in place in the slide channel. To hold the other end of each plunger in place, each guide portion 121 is made sufficiently long that it extend adjacent the cam follower portion of the other plunger, and each cam follower portion extends laterally over the forward edge of the guide portion 121 of the other plunger, thus preventing the two guide portions from moving forwardly. Rotative movement of the cam members 33 and 34 moves the cam surfaces 51 and 52 into engagement with the plungers 54 and 53, thus pushing the plungers and the movable contact arms 98 outwardly against the force of the spring action of the arms 98. When the cams are subsequently turned to move the cam surfaces 51 and 52 out of engagement with the plungers, the spring force of the arms 98 causes the switches to close again and the plungers to slide in the slide channel inwardly.

To install a limit switch control in a drive unit, the switch contact arms 92 and 98 are fastened in their enclosures, the covers 87 are placed over the enclosures, the plungers 53 and 54 are positioned in the slide channel, and the shaft 26 with the cam members attached thereto are mounted on the bearing posts. The screws 112 are then inserted through the holes in the covers 87 and the case 17 to secure the case to the housing 13 of the drive unit with the Worm 37 in mesh with the teeth 34. As shown in FIGS. 1, 2 and 4, openings 131 are formed in the housing 13 and in the cover 19, in axial alignment with the shaft 26, and the length of the shaft is preferably such that the ends of the shaft are recessed slightly from the outer surfaces of the housing 13 but nevertheless are accessible by a screwdriver inserted into the openings 131. The cover 19 is then fastened to the housing over the limit switch control, by the bolts 16.

The limit switch control may be used with a drive unit which has its power output shaft 12 connected to raise or lower a garage door, for example. The power output shaft 12 may be connected to the door such that the switch 22 is actuated by the cam 51 when the garage door reaches the upper position. To adjust the lower position of the garage door at which the motor 10 will be denergized, the first step may be to determine the distance of travel of the garage door caused by one revolution of the drive shaft 12. Then, the total number of revolutions of the shaft 12 to provide the desired adjustment may be determined. If it is decided, for example, that an adjustment equalling three revolutions of the shaft 12 is required, a screw driver is inserted into one of the slots 56 and rotary force is applied to turn the shaft 26 in one direction or the other, depending upon whether it is desired to increase or decrease the height of the garage door at which the motor 10 is to be turned off. Since the shaft 26 and the cam member 33 are axially stationary, except for slight movement due to play between the ridge 77 and the groove 78, and the cam member 34 is held against substantial rotation due to the engagement of the gear teeth 38 with the worm 37, the rotary force applied to the shaft 26 causes the cam member 34 to move axially away from the other cam member 33 as the teeth 41 and 42 pass each other. The fact that the gear teeth 38 extend axially and that the outer surface of the member 34, having the teeth 38 formed thereon is flat, enables the member 34 to move axially without interference due to the engagement of the teeth 38 with the worm 37. The ridges formed by the teeth 41 and 42 urge the two cam members 33 and 34 apart against the action of the spring 36, and a click will usually be heard as the teeth pass each other and reengage. Furthermore, since the angular distance between the teeth 41 and 42 is related in a one-to-one ratio with the gear ratio between the worm 37 and the gear teeth 38, rotation of the shaft 26 sufficient to cause 3 clicks will result in an adjustment equivalent to three complete revolutions of the shaft 12. Even if a click cannot be heard, the action of the teeth passing each other may be felt through the screw driver. As soon as the rotative force applied to the limit shaft 26 is removed, the teeth 41 and 42 will be held in mutual engagement by the force of the spring 36.

The limit switch control described has numerous advantages. For example, the relative positions of the two cam members 33 and 34 may be easily adjusted from outside the hOusing 13 making it unnecessary to remove the cover 19 in order to make an adjustment. Furthermore, an adjustment may be made either with or without power applied to the motor 10. Still further, an accurate adjustment may be made because of the relationship between the teeth 41 and 42, and the gear ratio between the worm 37 and the gear teeth 38, which produces one click for each revolution of the cam drive shift 12. Still another advantage of the construction is that a setting of the limit switch control is positive and relatively permanent. In other words, it is not easily changed by accident. Also, the limit switch setting will not be changed by vibration of the unit, by manual turning of the power output shaft of the motor unit, or through a careless adjustment of the unit.

The provision of a molded case on which the switches and the shaft 26 are mounted permits the limit switch control to be completely assembled before installation in a motor drive unit. Thus, a limit switch control in accordance with the present invention may be provided, which may be used with different types of drive units. Another principle advantage of the present limit switch control is that it permits the use of relatively in expensive easily manufactured switches.

I claim:

1. A limit switch control for a drive unit, comprising a one-piece molded case, a limit shaft connectable with said drive unit and rotatably mounted on said shaft for rotation therewith, at least one switch mounted on said case, said switch comprising a stationary contact member and a movable contact member which is movable into and out of electrical contact with said stationary member, and movable plunger means extending between and engageable with said cam means and said movable contact member of said switch, said case including a portion for supporting and guiding the movement of said plunger means and a portion for supporting said members of said switch, whereby rotative movement of said cam means said plunger means to move, and such movement of said plunger means causes said movable contact member of said switch to move into and out of contact with said stationary contact member.

2. Apparatus as in claim 1, wherein two switches and two plunger means are provided in said case, said two plunger means including interlocking portions which prevent them from accidentally falling out of said case.

3. Apparatus as in claim 1, wherein said movable contact member of said switch has an inherent spring force tending to hold said members in electrical contact, said cam means being adapted upon turning movement to move said plunger means and said movable contact member in one direction against said spring force, and continued turning movement of said cam means permitting said spring force to move said plunger means and said movable contact member in the opposite direction.

4. Apparatus as in claim 1, wherein said second mentioned portion of said case releasably holds said members of said switch.

5. A limit switch control for a drive unit, comprising a one-piece molded case, at least one switch fastened to said case, a limit shaft, said case including means formed integrally therewith for rotatably supporting said shaft, and cam means on said shaft for actuating said switch upon rotative movement of said limit shaft and said cam means, said rotatable mounting means comprising a bearing post adjacent each end of said limit shaft, a rounded depression formed in the outer end of each bearing post and said shaft being seated in said depressions, and a pair of clip posts adjacent each of said bearing posts and engaging said shaft, the clip posts of each pair being on opposite sides of said shaft and overlying said shaft, whereby said clip posts hold said shaft seated on said bearing posts.

6. Apparatus as in claim 5, wherein said clip posts are relatively flexible, whereby the clip posts of each pair may be flexed away from each other to permit said limit shaft to be mounted on said bearing posts and removed therefrom.

7. Apparatus as in claim 5, wherein said limit shaft has a circular groove formed in its outer periphery and a ridge is in said depression of one of said bearing posts, said ridge extending into said groove and preventing relative axial movement of said limit shaft.

References Cited UNITED STATES PATENTS 2,711,450 6/1955 Carr.

2,945,097 7/ 1960 Hake 20047 3,042,461 7/ 1962 Smith.

3,221,131 11/1965 Bury.

ROBERT K. SCHAEFER, Primary Examiner D. SMITH, J 11., Assistant Examiner U.S. Cl. X.R. 200168; 30837 

